Wave transmission system



April 15, 1947. w. J. ALBERSHEIM 2, 8,809

WAVE TRANSMISSION SYSTEM Filed Aug. 25, 1943 2 Sheets-Sheet 1 INVENTOR WJ ALBERSHE/M A TTORNE Y April 15, 1947. w J, ALBERSHElM 2,418,809

WAVE TRANSMISSION SYSTEM 2 Sheets-Sheet 2 Filed Aug. 25, 1943 FIG. 3

V /Nl/EN7'OR W J ALBERSHE/M A TTORNE Y similar Patented Apr. 15, 1947UNITED STATES PATENT OFFICE Walter J. Alcershe to Bell Telep New York,N.

Application August 25,

14; Claims.

elates to Wave transmission systems employing lar line structures-magnetic The invention 1' systems and particularly to dielectric waveguides or simi for transmitting high frequency electro waves.

An ohject of the invention is to connect secticns of dielectric waveguide or similar structure forming portions of a continuous transmissionline in such a system, so as to enable the total eiiective line lengthto be varied at will.

Another object is to couple two sections of dielectric wave guide orsimilar line str cture forming portions of a continuous transmissionline in a wave transmission system. so as to provide anadjustable-length ofiset between them having relatively low transmissionlosses.

These objects are attained in accordance with the invention by simpleand effective slide line joints. In one embodiment, a straight-lineslide joint is employed for coupling together two parallel wave guidesrespectively forming an input and an output transmission portion of anultrahigh frequency electromagnetic wave transmission system, so thatthe total length of transmission line may be varied at will, or forproviding an offset coupling between the input and output guides thelength of which may be readily adjusted to a desired value. Thisstraight-line slide joint may comprise another straight section ofsimilar wave guide made in two parts equivalent to those which would beformed by splitting a straight section of wave guide along itslongitudinal axis, so that the two coupling wave guide parts areslidable with respect to each other longitudinally. The two parts of thewave guide cou ling are respectively affixed at opposite ends to theinput and output wave guides, and two wave reflectors respectivelyaillxed to the input and output wave guides are angularly disposed withrespect to the complete cross-section of the wave guide coupling so asto reflect wave energy incoming over the input guide into the couplingguide and to reflect wave energy received over the coupling guide intothe output guide. Thus, the longitudinal sliding movement of either partof the coupling wave guide on the other part in either direction willchange the effective length of the coupling wave gu de and thus theamount of offset and the combined length of the connected. wave guidesections.

In another embodiment, the two parts of a wave guide coupling betweentwo sections of wave guide line or similar line structure, which make slding contact with each other or slide past each other, are bent alongparallel arcs of circles Interlahen, N. J., 'assignor hone Laboratories,Incorporated,

Y., a corporation of New York 1943, Serial No. 499,833

(01. Flti l) so as to provide a reciprocating rotary slide joint. Thevarious objects and features of the invenion will he better understoodfrom the following ta ed description when read in conjunction theaccompanying drawings in which: lg. 1 shows a perspective diagrammaticView of a portion of an ultra-high frequency electroagnetic wavetransmission system including one a 5 wave guide slide joint embodyingthe 4 ntial ieatures of the invention;

s. and 3 respectively show a perspective I a cross-sectional view of apractical embodiment or the form of wave guide slide joint diaiaticallyillustrated in Fig. 1; and l shows a perspective view of a portion of asi lar wave transmission system including another form of wave guideslide joint in accordance with the invention.

in the system of Fig. 1, the parallel elements identified as i and 2represent sections of dielectric wave guide, shown as consisting ofdivalent straight pieces of hollow metal pipe of rectangularcross-section, which may be input and output line portions,respectively, of a con- T uous transmission 1ine for transmittingultrai: gh frequency electromagnetic wave energy. The input wave guidesection I and the output wave guide section 2. are coupled by astraightwave guide slide joint CU consisting of a liar straight sectionof dielectric wave guide, as shown, may comprise a straight piece ofgular cross-section, rts 3 and 4 equivalent to the two halves of astraight piece of dielectric wave guide split along its longitudinalaxis, that is, along the line of zero current in the wave guide. Withthe wave guide slide joint or coupling CU so constructed, the contactingsurfaces 5, which slide past each other, indicated in l by doubleoutlines with exaggerated clearances, of the upper channel part 3 andthe lower channel part 4, respectively, of the coupling wave guide unit,are adapted for relative slidable movement longitudinally in eitherdirection.'

in any suitable manner, the lower end of the in ut wave guide i ispermanently affixed to the t end of he upper channel part 3 of thecoupling unit CU, and the upper end of the output wave guide 2 ispermanently affixed to the right end of the lower channel part 4 of thecoupling unit, so that the interior portions of the input wave guide Iand the output wave guide ii open into the interior portion of the waveguide coupling unit CU.

An angularly disposed reflector plate 1 (pref- I; hollow metal pipe ofrectan in two channel pa erably positioned at an angle of 45 degreeswith respect to the longitudinal axis of the coupling wave guide unitCU) having about the same width as that of the coupling unit, ispermanently affixed to the left end of the channel part 3 of thecoupling unit, and to the far lower pipe edge 8 of the input wave guideI. As shown through the broken-away side portion of the lower channelpart 4 of the coupling unit, the reflector plate 5 extends within theinterior portion of the latter channel part so that it provides areflecting boundary for the connected interior portions of the inputwave guide I and of the coupling unit CU. Similarly, the angular-1ydisposed (45-degree) reflector plate 9, having about the same width asthe coupling unit CU, is permanently aflixed to the right end of thelower wave guide part 4 of the coupling unit and to the right upper pipeedge of the output wave guide 2, and, as shown through the broken-awayside portion of the upper channel part 3 of the coupling unit CU,extends into the interior portion of the latter channel part of thecoupling unit, so that it provides a reflecting boundary for theconnected interior portions of the coupling unit CU and the output waveguide 2. Thus, for any relative positioning of the upper and lower waveguide parts 3 and 4 of the coupling unit CU, the reflector serves toreflect the electromagnetic wave energy received over the input waveguide I into that coupling unit and the reflector 9 serves to refiectthat electromagnetic wave energy received over the coupling unit intothe output wave guide 2.

It will be apparent, then, that by longitudinal movement of eithersliding wave guide part 3, l of the coupling unit CU, in one directionor the other, the offset distance between the parallel input wave guideI and output wave guide 2 may be increased or decreased by any desiredamount within the sliding range of the wave guide parts 3, 4, and thusthe effective length of the continuous transmission line including theinput wave guide I, the output wave guide 2 and the coupling unit CU maybe varied within the same limits.

Fig. 2 shows a perspective view, and Fig. 3 a cross-sectional view ofthat perspective view, of a portion of an ultra-high frequencyelectromagnetic wave transmission system, including a straight-line waveguide slide joint similar to that illustrated diagrammatically in Fig.1, corresponding elements in the two figures bearing the sameindentification characters.

In Fig. 2, the parallel input wave guide I and output wave guide 2 areshown as comprising straight hollow metal pipes with rectangularcross-sections, as in Fig. 1. The oppositely disposed identical channelparts 3 and 4 of the coupling unit CU in combination also form astraight hollow metal pipe wave guide with rectangular cross-section asin Fig. 1, but in Fig. 2 the longitudinally extending sides of the waveguide parts 3 and 4 of the coupling unit CU are shown as having adjacentoutwardly flanging portions Ill, I9 and I I, I I, respectively. To avoidsparking, resistance losses and standing waves in the two surfacessliding past each other, with or without an air-gap, due to the righfrequency current passing across the sliding surfaces, the so-calledlabyrinth construction is used, which does not necessitate the adjacentfianging portions of the coupling unit making direct contact with eachother.

As shown more clearly in the cross-sectional view of Fig. 3, which istaken along the lines timing AA looking toward the output wave guide 2in Fig. 2, the adjacent flanging portions II), III and II, I I onopposite sides of the two channel parts 3, 4 of the coupling unit areseparated alon their lengths by a substantial air-gap in the form ofstraight, meanderin grooves each a half wavelength deep, the ends ofeach groove being metallica-lly closed at one end P2 as shown. Fromtransmission line theory, it is known that at a distance of a half wave,that is, at the gap entrance point P1 (Fig. 3) there will be a voltagenode so that no sparking potential can exist. Half-way along eachgroove, at the quarter wave point P3," there will be a current node anda voltage maximum. The latter points along each side of the couplingunit are used for the actual bearing sliding surfaces. At this voltagemaximum, there is no voltage gradient across the slide surface, and,therefore, no current and no sparking. The flange surface it! on oneside of the channel portion 4 of the coupling unit is arranged to slidelongitudinally at such voltage maxima points along suitable bearingsurfaces, which may be formed from a commercial self-lubricatingmaterial, on the outer front rail piece I2 extending along the length ofthe coupling unit. The rail piece I 2 is attached firmly by screws I3 toa spacer block I4 also extending along the length of the coupling unit,which in turn is affixed in any suitable manner to one side of thechannel portion 3 of the coupling unit. Similarly, the flange portion IIon the opposite side of the channel portion 4 of the coupling unitslides longitudinally along suitable bearing surfaces at the voltagemaxima points, which bearin surfaces may be formed from a commercialself-lubricating material, on the back rail I2 extending along thelength of the coupling unit. The rail piece I2 is attached firmly byscrews I3 to a spacer block I4 also extending along the length of thecoupling unit, which in turn is affixed in any suitable manner to theside of the channel portion 3 of the coupling unit.

in tuning as they or portion of the will not be formed by the int toexactly the mice of reflection losses is convenient to provide inaccordquoncy band. As shown ay portion of the front rt l of the couplingun t .hrough a bearing 1pc side of the channel unit CU, and bearing rhector plate 7, provides means for .nguiar position of the reflectorstan. v

21198 with th s an 11 of the reflector p c other t cl of the couplingunit may a sted sl ntly Ly similar means not shown) A specificapplication of the straight line slide joint on" form of which isillustrated in igs. 1 to mi t he to provide an arrangement for 1e feedhorn across a parabolic ilO echo type object location sysantenna in ternin order to tilt the direction of the reflected beam.

Fig. 4 shows the application of the same design principle embodied inthe straight-line wave guide slide joint illustrated in Figs. 1 and 2,to reciprocating rotary motion, The arrangement shown differsessentially from that of Figs. 1 to 3 merely in that the two channelelement parts 3 and 4 of the wave guide coupling which make slidingcontact with each other or slide past each other, re in the sys 'l of 4bent to form parallel circular arcs o as to provide a reciprocatingrotary slide jo coupling the input wave guide l and the out; wave guide2, the angular position of the output wave guide with respect to theinput wave guide being varied as the distance between the two waveguides along the are of sliding movement varied in one direction or theother. To prevent sparking, resistance losses and standing waves due tothe high fre quency current across the riding surfaces, these 4 .an beprotected by half wave grooves a actual bearing surfaces located atquarter i we points like those illustrated in detail in the arrangementof Figs. 2 and 3, as indicated diagrammatically in Fig. 4. One practicalapprlcation or the arrangement of Fig. i would be to serve as a feedconnection to a rocking paraboloid antenna, where the location of arotary joint at the rocking axis is isechann oally impractical.

In the form of the invention shown in Figs. 1 and 2,. the variablelength section of wave guide providing the coupling unit is split alongthe line of zero current. A mechanically more compact form of this sametype of wave joint may be olotained by turning the wave guide on edge sothat it is divided across the center line oi? the short walls. ihiscenter line would have a high cur-- rent density which might introducesparking, sistance losses and standing waves, but these may be preventedif the between the elements which slide past each other are bridged byquarter wave grooves in the manner described above. Other modificationsof the circuits illustrated and described which are within the spiritand scope of the invention will occur to persons skilled in the art.

What is claimed is;

1. In an electromagnetic wave transmission system, two dielectric waveguides forming portions of a continuous wave transmission line andvariable length wave coupling means between said two wave guidescomprising a third d electric wave guide divided longitudinally into twoparts adapted for relative slidable movement longitudinally, one of saidtwo wave guides being fixedly connected to one end oi one of said partsand the other being fixedly connected to the opposite end of the otherpart of said third wave guide, so that the length of the wavetransmission path between said two wave guides over said coupling meansmay be varied by said relative slidable movement of said two wave guideparts, and wave deflecting means respectively fixedly connected to adifferent one of said two wave guides, for diverting the wave energyreceived over one of said two wave guides into said third coupling waveguide and that energy from the latter wave guide into the other of saidtwo wave guides.

2. The system of claim 1, in which the twopart third dielectric waveguide comprises a straight hollow metal tube split longitudinally alongits center line to form a straight line slide joint coupling betweensaid two dielectric wave guides.

3. The system of claim 1, in which the two-part third dielectric waveguide comprises a hollow metal pipe of rectangular cross-section, curvedso that its longitudinal axis is in the arc of a circle, said metal pipebeing split into two identical channel parts along said longitudinalaxis, the reciprocating rotary slidable movement of said two wave guideparts relative to each other providing means for varying the couplingdis tance between said two wave guides along said longitudinal axis.

4. A variable-length coupling arrangement for use between two tubularwave conductors forming sections of a continuous transmission line fortransmitting high frequency electromagnetic wave energy, comprising athird tubular conductor made in two parts such as would be formed bysplitting a similar conductor along a plane parallel to its longitudinalaxis, so as to permit relative slidable motion longitudinally betweensaid two parts, each of the first two conductors being respectivelyconnected to a different one of said two parts of said third tubularconductor at opposite ends thereof, so as to be movable longitudinallywith that part and to be in waveltransmitting relation with said thirdtubular conductor, and wave transferring means respectively fixedlyconnected to a difierent of said two conductors and being disposedacross the crosssectional area of said third conductor so as torespectively direct the wave energy received over one of said .twoconductors into said third conductor and that wave energy transmittedover said third conductor into the other of said two conductors.

5. In a high frequency electromagnetic wave transmission system comp sng several tubular wave conductors forming sections of a continuous wavetransmission line, means for enabling the effective length of saidcontinuous line to be varied within certain limits, comprising a thirdtubular wave conductor of a given length, having two separate partsequivalent to those which would be produced by splitting a similar waveconductor along a plane parallel to its longitudinal axis, so as topermit relative slidable movement longitudinally between said two parts,said third tubular conductor coupling two successive ones of saidseveral tubular line conductors in wave-transmitting relation with eachother, one of said two successive wave conductors being fixedlyconnected to one end of one of said two parts and the other of said twosuccessive conductors being fixedly connected to the opposite end of theother of said two parts of said third conductor, so as to berespectively movable longitudinally with movement of the connected part,and reflector means respectively fixedly connected to one of said twosuccessive conductors and angularly disposed across the cross-sectionalarea of said third tubular conductor at opposite ends thereof, saidreflector means respectively serving to reflect wave energy receivedover one of said two successive tubular conductors into said thirdconductor and to reflect that wave energy transmitted through said thirdconductor into the other of said .two successive tubular conductors.

6. The system of claim 5, in which said two successive tubular conductorare in parallel with each other and said third conductor provides meansfor obtaining anadjustable length offset coupling between them.

'7. The coupling arrangement of claim l in which each of said twotubular wave conductors and said third tubular conductor comprises ahollow metal pipe forming a dielectric wave guide, the hollow metal pipeof said third tubular conductor being split along its longitudinal axisto form two identical parts adapted for sliding past each otherlongitudinally in one direction or the other to adjust the efiectivelength of the coupling between said two conductors, and said wavetransferrin means comprise two metal plates each having one edge fixedlyconnected to the far pipe edge of a diiierent one of said first twoconductors and extending angularly across the end of the pipe part ofsaid third conductor connected thereto into the interior of the otherpipe part of aid third conductor, so as to be movable longitudinallytherein with relative longitudinal movement of the two pipe parts.

8. The coupling arrangement of claim 4, in which said third conductorcomprises a straight length of hollow pipe of rectangular cross-section,split into two parts in a plane along the longitudinal axis, theconnection of the respective parts of said pipe to said two waveconductors being such that the interior portions of said pipe and thoseof said two tubular conductors open into each other 9. In combination ina wave transmission system, dielectric wave guide split longitudinallyinto two norv apt-ed for relative slidable movement loi an input waveguide *1 an output e guide coupled in wave-transg relation with thefirst wave guide, said input wave gui being fixedly connected to one endof one of wave guide portions and said output wave guise i ng fixedlyconnected to the opposite of the other wave guide portion, so hat theeffective wave transmission distance between said input wave guide andsaid output wave uide varied h" relative longitudinal en the two waveguide portions e and means for deflectived over said input wave oversaid first wave guide into said out ut wave guide.

10. The comhina 'ion of claim 9 in which said wave guide is splitlongitudinally along a svaight line so that it provides a straight-line8 slide joint coupling between said input and output wave guides.

11. The combination of claim 4, in which said third tubular conductorcomprises a straight hollow metal pipe of rectangular cross-sectionsplit longitudinally into two identical parts along a horizontal planemidway between its short walls so as to enable straight-line slidablemovement between the two parts in either direction to vary the effectivelength of the wave transmission path between d two tubular conductorsthrough said straight hollow metal pipe, and means to prevent sparkingand resistance losses in said coupling arrangement due to the highfrequency current passing across the slide surfaces of said identicalwave parts.

12. The system of claim 5, in which each of said tubular wave conductorscomprises a straight piece of hollow metal pipe of rectangularcrosssection, the straight hollow metal pipe forming said third tubularconductor being divided into two parts longitudinally along the line ofzero current.

13. The system of claim 5 in which all of said tubular conductorscomprise straight hollow meta1 pipes of rectangular cross-section, thehollow metal pipe forming said third tubular conductor being dividedinto two identical portions across the center line of the short walls,said two identical portions being spaced from each other along theirlength by an appreciable air-gap, and being adapted for relativeslidable movement longitudinally to vary the wave transmission distancebetween the hollow metal pipes comprising said two successive conductorsover the first hollow metal pipe.

14. The system of claim 9, in which said input and said output waveguides comprise straight pieces of hollow metal pipe, and said firstdielectric wave guide comprises a hollow metal pipe bent so that itslongitudinal axis is curved in the re of a circle with the relativeslidable movement of the two portions thereof being a rotaryreciprocating one.

WALTER J. ALBERSHEIM.

